On 12/17/21 03:30, David Hildenbrand wrote:
> Let's return early for hugetlb, which really only relies on the compound
> mapcount so far and does not support PageDoubleMap() yet. Use the chance
It is too early to say if hugetlb double mapping will use PageDoubleMap().
I do not think (hope) it will be necessary. So, I think you can drop mention
of it here.
> to cleanup the file-THP case to make it easier to grasp. While at it, use
> head_compound_mapcount().
>
> This is a preparation for further changes.
>
> Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
--
Mike Kravetz
> ---
> mm/util.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/mm/util.c b/mm/util.c
> index 741ba32a43ac..3239e75c148d 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -732,15 +732,18 @@ int __page_mapcount(struct page *page)
> {
> int ret;
>
> - ret = atomic_read(&page->_mapcount) + 1;
> + if (PageHuge(page))
> + return compound_mapcount(page);
> /*
> * For file THP page->_mapcount contains total number of mapping
> * of the page: no need to look into compound_mapcount.
> */
> - if (!PageAnon(page) && !PageHuge(page))
> - return ret;
> + if (!PageAnon(page))
> + return atomic_read(&page->_mapcount) + 1;
> +
> + ret = atomic_read(&page->_mapcount) + 1;
> page = compound_head(page);
> - ret += atomic_read(compound_mapcount_ptr(page)) + 1;
> + ret += head_compound_mapcount(page);
> if (PageDoubleMap(page))
> ret--;
> return ret;
>
